Hydrocarbon in water emulsions are well known and have a variety of uses, e.g., as fuels for power plants or internal combustion engines. These emulsions are generally described as macro-emulsions, that is, where the emulsion is cloudy or opaque as compared to micro-emulsions that are essentially clear, translucent, and more thermodynamically stable than macro-emulsions, the micro-emulsions having a higher level of surfactant.
While aqueous fuel emulsions are known to reduce pollutants when burned as fuels, the methods for preparing emulsions and the materials used therein, e.g., surfactants and co-solvents, such as alcohols, can be expensive Also, the thermodynamic stability of macro-emulsions is relatively weak, particularly when low levels of surfactants are used in preparing the emulsions.
Consequently, there is a need for stable macro-emulsions that employ less surfactants or co-solvents, and use less costly materials in preparing hydrocarbon in water emulsions. Additionally, by virtue of the invention described herein, distillate fuel emulsions of conventional petroleum fuels can be upgraded, for example, to higher cetane index, by blending with Fischer-Tropsch derived hydrocarbon liquids, e.g., distillates.
For purposes of this invention, the stability of macro-emulsions is determined generally as the degree of separation occurring during a twenty-four hour period, usually the first twenty-four hour period after forming the emulsions.